Almost as many people travel on buses in this country as fly on airplanes, yet tour buses are only loosely regulated. Unlike planes, they’re involved in accidents all the time.

That’s especially true of buses that take people to and from casinos, which are part of a booming business these days.

At the vast San Manuel Indian Bingo and Casino east of Los Angeles, gamblers crowd around the roulette table and try their luck at blackjack, or one of the thousands of slot machines. If you walk through the smoky haze, past the window where you cash in your chips -- if you’re lucky -- you reach an area called the Bus Lobby where coaches line-up. Those buses pick up and drop off gamblers, whisking them to almost 30 stops in Southern California.

“You go to a casino nowadays and it looks like an inter-city bus station,” says Dr. Joseph P. Schwieterman, a transportation expert at DePaul University in Chicago. “You look at the size of the sector and you see it as really exploding. It’s pretty remarkable that we have this whole public transit system in the United States feeding these casinos. The bus industry at the casinos has just been hand-in-hand.”

But the casinos don’t see it that way. They prefer keeping the bus companies at arms-length, casting them off as merely independent operators.

“I think they are intentionally turning a blind eye to the dangers that these buses create for these customers,” says Katherine Harvey-Lee, a lawyer who’s represented bus accident victims.

She points out that most casinos post their bus schedules online, for everyone to see.

“You’ve put them on your website and I think by doing so you’re impliedly endorsing these as a safe way of getting to your casino,” says Harvey-Lee.

In August, a bus on its way to San Manuel crashed after the driver made an unsafe lane change. More than 50 people were hurt.

Last month, three casino buses crashed in five days on Southern California roads.

But one of the worst casino bus accidents happened three years ago in the Bronx, killing 15 people.

California has the most tour bus operators in the nation – some 400 according to the National Transportation Safety Administration – and yet a recent federal crackdown resulted in just one California carrier getting shut down.

Katherine Harvey-Lee finds that appalling.

“It would be totally unacceptable if you had an airline that was constantly getting safety violations and had airplanes that didn’t even have seatbelts, and was still allowed to operate,” says Harvey-Lee. “The reality is that buses carry almost as many people as our aviation industry, but we’re not paying as close attention to the safety issues.”

After the Bronx crash, Washington lawmakers held hearings, but the accidents continued.

The agency that regulates buses, The Federal Motor Carrier Safety Administration, has been repeatedly criticized for not doing enough to keep unsafe buses off the road. Last November, the National Transportation Safety Board called for an audit of the agency's practices.

"While FMCSA deserves recognition for putting bad operators out of business, they need to crack down before crashes occur, not just after high visibility events," says NTSB Chairman Deborah A.P. Hersman in a statement. "Our investigators found, that in many cases, the poor performing company was on FMCSA's radar for violations, but was allowed to continue operating and was not scrutinized closely until they had deadly crashes."

But FMCSA has had limited power since 2005, when Congress passed legislation that included a ban on surprise roadside inspections.

“Literally it was something that was stuck in the transportation bill at the last minute,” says Stephen Keppler, Executive Director of the Maryland-based Commercial Vehicle Safety Alliance. “We didn’t see it until it was already in the bill. From our perspective, something this significant clearly was motivated politically. Really, safety wasn’t considered.”

FMCSA says it was still able to inspect more than 850 buses at about 100 different surprise inspection points in California alone last year. But the surprise inspections can’t take place while a bus is in transit, which Keppler says makes a crucial difference.

“Frankly, it’s had a huge impact on enforcement’s ability to do an effective job of policing the highways regarding unsafe motor coach operators,” says Keppler.

If law enforcement wants to inspect buses at a casino, officers have to call ahead and ask permission to come onto the property.

Among those who pushed to stop the surprise roadside inspections was the American Bus Association, which argues the inspections are unsafe for passengers.

“If you do a bus inspection on the side of the road the fifty people on the bus have to get off the bus,” says Dan Ronan, Senior Director of Communications, Media and Marketing for the American Bus Association. “They don’t have restroom facilities. They don’t have water. What we believe is that bus inspections need to be done at the location the bus companies are operating out of. You don’t stop an airplane at 35,000 feet and pull the airplane over and do an inspection of an aircraft. You do an inspection at the airport or the hangar.”

Trouble is, it’s difficult for law enforcement – let alone riders – to know something as simple as which company is operating which bus.

“They are transient and they are difficult to locate, and some of them are evading us, for good reason, says Jeff Picardi, who helps oversee tour bus enforcement at the California Highway Patrol. “For the personnel that we have, and the resources we have, we struggle, frankly.”

One carrier gets banned, and a couple weeks later another pops up with the same owners. They’re known in the industry as “chameleon carriers.”

“The sands are shifting all the time,” says Harvey-Lee, the lawyer who represents bus accident victims. “The buses are continuously being leased to other companies, however it suits them to evade regulation and evade inspectors.”

Regulators and lawmakers have tried for years to bring back surprise roadside inspections, but haven’t gotten anywhere. After last February’s tour bus crash in San Bernardino that killed 8 people, U.S. Rep. Gloria Negrete McLeod proposed a bill, which would allow in route inspections. That bill is stuck in committee.

No casino would agree to an interview for this story, but we did speak to a bus operator, Anthony Wen, who runs 15 trips a day to Los Angeles-area casinos.